I do get a small continuous flow of fuel from the carb bowl whenever I pull the plug from the bottom. The engine oil is at the proper level. This unit only has 3 to 4 hours run time on it.

The unloader assembly seems to be working properly as it opens when I release the nozzle trigger (the engine "unloads") although sometimes I get a pressure lock and must release water pressure via the trigger before I can pull start the engine.

I do know there's a low oil pressure switch on the engine and thought it might be the culprit (warm engine and the lower oil viscosity produces a lower oil pressure) - I tried shorting out the switch but it didn't seem to do anything (maybe that's not the right way to check it ?)

So I'm now at a loss as to what to try next. Any suugestions ?

It is an overhead valve engine with a prominent valve cover marked OHV.

Never did. Tried loosening my fuel cap. Checked for fuel flow at the carb (plenty). Emptied my fuel and reloaded with fresh - still same problem.

Haven't had a chance to play with it since then, it sits in the back of my garage as a reminder of projects needing to be done :-)

I do suspect an ignition module as Canguy suggested and maybe it's that pressure switch I've never gotten any more info on. So I would still like some further suggestions myself.

If you come up with anything please publish it.
Richard

I will say that I felt my problem was a fuel problem because of how easy it would start after each stall. If the problem was heat related, I would expect more time would be required to let things cool down before it would start again.

>Craftsman 3100 PSI Pressure Washer Model 580.752080 purchase new in 2007
>Briggs & Stratton 121012-0123-B1 900 Series Single Cylinder OHV 4 cycle (no fuel pump or filter)
>No more than 20 hours of use on it.

This is how I diagnosed the problem:

The gas tank has a shut off valve. Closed that and disconnected the fuel hose from the carb. Removed the gas tank from the pressure washer. Held the tank over a gas container and opened the shut off valve. Gas started draining and then got slower and slower until it stopped draining, even though the tank was still full. Loosened the cap and the gas started flowing again.

After draining the tank, I tightened the gas cap and put compressed air at the fuel hose. No air leak.

So my guess as to what was happening is:

The carb bowl has gas and no vacuum exists in the tank. On first start, engine runs for about 5 minutes under full load and then stalls. The stall is caused because vacuum has built up in the tank and there is not enough fuel flow to serve the engine's need under load. The carb bowl empties and the engine stalls. Now the engine sits for a minute. Gas trickles into the carb bowl. On second start, the engine fires up but sucks the carb bowl dry again. (By the way, it will run for a long time if not under load. Probably because it doesn't require as much fuel flow.)

I inspected the cap design closely and it has no vent hole. I'm not sure why the cap worked and now it doesn't. Guessing there was something there that prevented the cap from screwing down too far, and over time it wore down. I didn't see anything on the tank either that would suggest a design for venting.

Anyway, now I screw on the cap so it is almost loose and the pressure washer has worked all afternoon under full load with no stalls. Go figure.